Biochemical and clinical response to hydroxocobalamin versus cyanocobalamin treatment in patients with methylmalonic acidemia and homocystinuria (cblC).
OBJECTIVE
To compare the therapeutic effectiveness of hydroxocobalamin and cyanocobalamin in patients with combined methylmalonic acidemia and homocystinuria.


METHODS
Analysis of urine methylmalonic acid, plasma homocystine, and growth of two unrelated patients with cobalamin C disease who were initially receiving cyanocobalamin and were subsequently switched to hydroxocobalamin.


RESULTS
Each patient had a significant decrease in urine methylmalonic acid excretion while receiving cyanocobalamin, but levels remained at least 10 times normal. Cyanocobalamin treatment resulted in a decrease of plasma homocystine to near normal in one patient but had no effect on plasma homocystine in the second patient. Each patient was switched to hydroxocobalamin and urine methylmalonic acid levels decreased to the limit of detection. Plasma homocystine values while taking hydroxocobalamin remained < 5 nmol/ml in both patients. In patient 1, who continued to receive cyanocobalamin therapy for more than 1 year, growth rates (height, weight, and head circumference) were very poor. After initiation of hydroxocobalamin, growth parameters normalized with growth rates above normal.


CONCLUSIONS
Intramuscular cyanocobalamin treatment is inadequate in the treatment of patients with cobalamin C disease. Appropriate management of cobalamin C disease should include only the hydroxocobalamin form of cobalamin.
Andersson
H C
HC
Human Genetics Program, Tulane University School of Medicine, New Orleans, Louisiana 70112, USA.
Shapira
E
E
D002648:Child; D002675:Child, Preschool; D005260:Female; D006128:Growth; D006711:Homocystine / Q000097:blood*; D006712:Homocystinuria / Q000188:drug therapy / Q000503:physiopathology; D006801:Humans; D006879:Hydroxocobalamin / Q000627:therapeutic use*; D007223:Infant; D008297:Male; D008661:Metabolism, Inborn Errors / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology / Q000652:urine; D008764:Methylmalonic Acid / Q000378:metabolism* / Q000652:urine; D014805:Vitamin B 12 / Q000627:therapeutic use*
D006711:Homocystine; D008764:Methylmalonic Acid; D014805:Vitamin B 12; D006879:Hydroxocobalamin